1. Field of the Invention
The present invention relates to an anti-collision method system in a wireless network system. More particularly, the present invention relates to an anti-collision method and system in a wireless network system taking into consideration the efficiency of a multicast data transmission.
2. Description of the Related Art
FIG. 1 is a view illustrating a collision process in a wireless network system according to the prior art. Referring to FIG. 1, a first device 1 transmits predetermined data to a second device 2. The second device 2 receives the predetermined data from the first device 1 and then transmits an ACK signal. A third device 3 at one hop distance from the second device 2 as well as the first device 1 receives the ACK signal from the second device 2. In a case where a fourth device 4 accidentally transmits predetermined data to the third device 3 in the same time interval, a collision occurs in the third device 3.
The fourth device 4 transmits predetermined data to the third device 3. The third device 3 receives the predetermined data from the fourth device 4 and then transmits an ACK signal. The second device 2 at one hop distance from the third device 3 as well as the fourth device 4 receives the ACK signal from the third device 3. In a case where the first device 1 accidentally transmits predetermined data to the second device 2 in the same time interval, a collision occurs in the second device 2.
FIG. 2 is a view illustrating a principle of an anti-collision method in a wireless network system according to the prior art. A conventional anti-collision method for preventing a collision described with reference to FIG. 1 will now be described with reference to FIG. 2. A second device 2 receives data from a first device 1 and then transmits an ACK signal. The second device 2 also transmits to a third device 3 a beacon signal including information related to an allocated time interval added to a time interval in which the second device 2 receives data from the first device 1 and a time interval in which the second device 2 transmits the ACK signal.
The third device 3 transmits to a fourth device 4 a beacon signal including information related to a time interval in which the third device 3 receives the beacon signal from the second device 2 and a time interval in which the third device 3 transmits the ACK signal added as allocated time intervals to the information related to the allocated time interval received from the second device 2. Thus, the information related to the allocated time intervals can be transmitted to a neighboring node so as to prevent the collision described with reference to FIG. 1.
Here, devices inform neighboring devices at one hop distance of information related to time intervals allocated to them through a distributed reservation protocol information element (DRP IE) and devices at two hop distances of the information through a DRP availability IE.
However, the prior art assumes a unicast data transmission requiring an ACK response. Thus, even in a case of multicast data transmission not requiring an ACK response, a time interval necessary for the ACK response is identified as an allocated time interval.
Accordingly, in the case of multicast data transmission, substantially available time intervals are regarded as time intervals necessary for an ACK response. Thus, a time interval for an anti-collision is inefficiently allocated.